I just looked in the trash and found
THIS!The three music files belong; I just trashed them. But everything else in there was trashed immediately after I reran the 10.15.5 Combo on
June 24th, and I've emptied the trash countless times since then.
And beyond that, because those items are all system items that are protected by macOS they were trashed while I was booted into a different volume. (Hmmm... To which trash did they go?)
Anybody ever seen anything like it?